The broad aim of this collaborative study is to examine the interrelationships or patterns of activity of some aspects of a number of biological systems or variables (adrenergic, serotonergic, neuroendocrine, enzyme and electrolyte) considered important in the genesis or continuation of altered affect in depressed patients. We wish to compare the interrelationships of these systems as found in depressed patients with other diagnostic categories (hospitalized schizophrenics or acute, nonaffective, undiagnosed psychosis, hospitalized personality disorders, hospitalized patients undergoing neurological workup but found devoid of neurological disease, and nonhospitalized normals) as control groups. Particular attention will also be given to ascertaining relationships between combinations of biological variables (patterns) and diagnostic categories or subgroups, subsequent response to treatment, state variables (especially depression, anxiety, activity), family history data and plasma levels of antidepressant drugs and their metabolites. This collaborative study is unique in that it allows simultaneous focus on a number of important biological systems in a large number of carefully and consistently selected study patients and comparison (control) groups. Therefore, testing of hypotheses about biological variables currently considered important can be done in a manner not previously available. The success of this type of collaborative study, using the individual but synthesized expertise of a number of geographically separate groups, will act as a model for subsequent biological behavioral collaborative studies.